The present invention generally relates to surgical devices adapted to capture an object within a cavity of the human body, such as when moving, manipulating and extracting biological material during a medical procedure. More particularly, this invention relates to a surgical device comprising elongate members that, when collapsed toward each other, are capable of capturing an object, and wherein each of the elongate members has a cross-sectional shape that promotes the ability of the elongate members to expand and collapse relative to the other members.
Various instruments are known in the art for surgically removing stones, calculi and other hard materials from the body. An example is an extraction instrument disclosed in U.S. Pat. No. 5,281,230 to Heidmueller as comprising a pair of bowls that are pivoted toward and away from each other by engaging their proximal ends with a sheath. Other types of extraction instruments make use of multiple wires that are flexed to grasp an object. For example, U.S. Pat. No. 5,944,728 to Bates discloses an instrument having arcuate wires with rectangular, round, D-shaped, or V-shaped cross-sections. The wires form a basket when a plunger associated with the instrument is in a distal position, allowing the legs to radially collapse toward each other. To expand the legs, the plunger must be actuated into engagement with the legs, forcing the legs radially apart from each other. As such, surgically moving, manipulating and extracting material from a body cavity is complicated by the requirement to additionally operate the plunger to expand and contract the legs.
Another example of an extraction instrument is disclosed in U.S. Pat. No. 6,203,552 to Bagley et al. As with Bates, the instrument taught by Bagley et al. has arcuate legs that form a collapsible basket when actuated with respect to a sheath. Each leg has a wedge-shaped cross-sectional shape, so that together they fill the cross-sectional area of the sheath. Contrary to Bates, the instrument disclosed by Bagley et al. does not require a separate plunger to expand (dilate) and collapse the basket.
U.S. Pat. No. 6,500,182 to Foster and U.S. Patent Application Publication No. 2002/00668954 to Foster disclose other extraction instruments configured to be actuated without the assistance of a plunger. Each instrument taught by Foster has resilient grasping members (legs) that form a basket or forceps when extended from a sheath, and which collapse toward each other when the sheath is advanced over the legs (or the legs are retracted into the sheath). According to Foster, the legs are formed by cutting or forming slots in an elongated cylindrical member, such as a cannula. If formed from a cannula, the legs are said to have semicircular cross-sectional shape. The edges of the legs are said to be spaced apart when in the compact (collapsed) position, a condition which appears to be inherent because each adjacent pair of legs is separated by the slot formed during the cutting/forming operation that defined the legs. As such, it appears the legs cannot be fully collapsed with the sheath, since the sheath cannot have an inner diameter smaller than the cannula from which the legs were defined and which must also be accommodated within the sheath.
There is an ongoing effort to devise surgical extraction instruments with greater dilating force when expanding to acquire an object, with greater grasping strength when capturing onto an object, and that maintain their form and alignment throughout their range of motion so as to more easily capture biological material during a variety of medical procedures.